1. Field of the Invention
The present invention relates to an ultrasonic endoscope whose insertion portion includes a distal hard portion which has an endoscopic observation unit having an observation field of view forwardly of the endoscopic observation unit, and an electronic scanning type of ultrasonic observation unit having a circular or arcuate ultrasonic scanning plane perpendicular to the axis of the distal hard portion.
2. Description of the Related Art
A so-called electronic scanning type of ultrasonic endoscope has heretofore been widely used in which endoscopic observation means for observing a body cavity, an endoscopic mechanism including other means such as a treatment equipment insertion path through which to insert forceps or other treatment equipments, and ultrasonic observation means are fitted in a distal hard portion of an insertion portion and the ultrasonic observation means performs scanning by sequentially driving a multiplicity of ultrasonic transducers arranged in a predetermined direction in the ultrasonic observation means. For example, JP-A-2001-314403 describes a direct-view endoscope which has a field of view forwardly of a distal hard portion of its insertion portion as an observation field of view in the endoscopic observation means and in which the ultrasonic observation means has an ultrasonic scanning plane in its radial direction, i.e., a circular ultrasonic scanning plane or an ultrasonic scanning plane which is arcuate in a predetermined angular range.
The ultrasonic endoscope described in JP-A-2001-314403 is inserted into a body cavity tube, for example, an upper gastrointestinal tract such as the esophagus or the small intestine, or a lower gastrointestinal tract such as the large intestine, and an area which appears forward in the insertion direction is observed by the endoscopic observation means. If an area of interest such as a lesion is detected, the ultrasonic observation means is positioned to face the area of interest so that information about body tissues in the area can be acquired.
In the above-described type of ultrasonic endoscope, the number of ultrasonic transducers constituting an ultrasonic transducer array is made several tens or more in terms of resolution. Cables are respectively connected to electrodes of the ultrasonic transducers, and the connection of the cables to the electrodes is generally provided via a flexible circuit board made of a resin film. In the JP-A-2001-314403, the flexible circuit board is divided into a plurality of flexible circuit boards, and each of these flexible circuit boars is extended to an intermediate position in the insertion portion and is connected to a respective one of the cables. The insertion portion has a structure in which an angle portion and a flexible portion are sequentially joined to the distal hard portion fitted with the endoscopic observation means and the ultrasonic observation means, and the connection between the flexible circuit boards and the cables is provided at a position inside the flexible portion extended from the angle portion. Proximal ends of the flexible circuit board to which the respective cables are connected are placed in a free state.
In this construction, when the ultrasonic observation means is to be incorporated into the insertion portion, the ultrasonic observation means is inserted into the insertion portion with the cable connected to the flexible circuit board in advance, and the proximal ends of the cables are inserted by being drawn from the proximal side of the insertion portion, until the ultrasonic transducer array is arranged at the distal end of the insertion portion. The flexible circuit board needs to have a certain degree of rigidity in order to ensure the stability of connection of the cables to the flexible circuit board, so that during insertion into the insertion portion, the flexible circuit board is inserted while its side edges are being caught on other members, and insertion operationality is degraded. In addition, if the cables are operated while being extremely strongly pulled, there is a risk that the cables are broken.
In addition, since the ultrasonic observation means and the endoscopic observation means are incorporated in the insertion portion, the inside of the insertion portion has a high filling factor. Since the angle portion is sharply bent by a bending operation, the end of the angle portion is brought to a free state, and the flexible circuit having a certain extent of rigidity is forcedly folded during the bending of the angle portion, and the end is forced against another member, for example, a light guide constituting the endoscopic observation means, and an edge of the end may break the light guide made of a very thin optical fiber or a cable connected to a solid-state image pickup device. Furthermore, a treatment equipment insertion tube or an air/water feed tube is buckled or damaged, and other problems occur.
In other words, in the case where the flexible circuit board is used when the cables are respectively connected to a multiplicity of ultrasonic transducers, if part of the flexible circuit board is placed into a free state, an edge or corner section of the flexible circuit board which is placed in a free state interferes with other members and compresses or damages these members not only during the incorporation of the insertion portion but also during the operation of the ultrasonic endoscope.
The invention has been made in view of the above-described problems, and an object of the invention is to ensure the fixability and stability of cables connected to an ultrasonic transducer array and makes it possible to facilitate incorporation of endoscopic observation means into an insertion portion.
An ultrasonic transducer array is generally made of an approximately cylindrical unit, and a backing layer is arranged in the inside of ultrasonic transducers, while an acoustic lens is fitted on the outside of the ultrasonic transducers. The acoustic lens serves to focus ultrasonic beams transmitted from the ultrasonic transducers, and beams in directions perpendicular to an ultrasonic-wave transmission plane are improved by the acoustic lens. The ultrasonic transducer array is integrated with the above-mentioned members and the like and is incorporated in the distal hard portion of the insertion portion, and each member constituting the endoscopic observation means and the like is inserted through the inside of the ultrasonic transducer array formed in a cylindrical shape in this manner, specifically, a tunnel-shaped path formed in the inside of the backing layer.
The insertion portion of the ultrasonic endoscope is inserted into the body of a subject for the purposes of various examinations and treatments, so that the diameter of the insertion portion need be made as thin as possible. If the accuracy of examination by the ultrasonic observation means is to be increased, it is necessary to increase the size of each of the ultrasonic transducers so as to increase the output power thereof. Accordingly, not only the thickness of each of the ultrasonic transducers increases, but also the thickness of the backing layer must be increased. The endoscopic mechanism is inserted in the tunnel-shaped path formed in the inside of the backing layer.
The endoscopic mechanism needs at least an illumination section and an observation section because the endoscopic mechanism is used to optically observe body cavities. There is also a case where other members such as a treatment equipment insertion channel and a cleaning-fluid supply tube for an observation window are provided in the endoscopic mechanism. In the observation section in particular, there is a case where an objective lens and a solid-state image pickup device as well as, if necessary, various filters and a prism for bending an optical path are provided. The treatment equipment insertion channel is constructed to allow forceps and other treatment equipments to be inserted through, and is desirably made of a thick tube in order to allow insertion of large-sized treatment equipments.
As described above, the ultrasonic endoscope has the problem that if any of the functions of the ultrasonic observation means or the endoscopic mechanism is to be improved, the insertion portion must be made thick as needed. The inside diameter of the backing layer in particular has an extremely large influence on the fitting of the endoscopic mechanism. An object of the invention is to make it possible to ensure a wide fitting space for the endoscopic mechanism by making as wide as possible the cross section of the tunnel-shaped path formed by the backing layer.